Filter circuit device and method of manufacturing the same

ABSTRACT

This invention is a filter circuit having a filter element. A filter element ( 4 ) is a parallel resonator circuit including a pair of first resonator lines ( 19   a ) ( 19   b ) formed by a thick film forming technique and a pair of second resonator lines ( 20   a ) ( 20   b ). As the thickness of the pair of second resonator lines ( 20   a ) ( 20   b ) is significantly reduced, the impedance ratio between the pair of second resonator lines ( 20   a ) ( 20   b ) and the pair of first resonator lines ( 19   a ) ( 19   b ) is increased. Therefore, the length of these pairs of resonator lines ( 19   a ) ( 19   b ) ( 20   a ) ( 20   b ) is reduced and miniaturization of the filter element is realized.

TECHNICAL FIELD

This invention relates to a filter circuit device having a filterelement and a method for manufacturing the same.

This application claims priority of Japanese Patent ApplicationNo.2001-397677, filed on Dec. 27, 2001, the entirety of which isincorporated by reference herein.

BACKGROUND ART

Recently, in high-frequency applications using a microwave band or amilliwave band as a carrier, for example, in wireless LAN or variouscommunication terminals, reduction in size and thickness of equipmentand circuit board has been demanded. In a circuit board for suchhigh-frequency applications, filter elements such as a low-pass filter(LPF), a high-pass filter (HPF) and a band-pass filter (BPF) aredesigned with a distributed constant, for example, using a microstripline or a strip line that enables relatively high space-saving, insteadof using a lumped constant design using chip components like an inductorand a capacitor.

For example, a circuit board 100 shown in FIG. 1 has a BPF 101 of a flatstructure, as a filter element designed with a distributed constant. Inthis circuit board 100, conductor patterns 103 made of copper or nickelplated with gold are formed as microstrip lines on a dielectric board102 such as a printed board or a ceramic board, thus constituting theBPF 101. On the entire back side of the dielectric board 102, a groundpart (not shown) is formed.

With such a BPF 101, it is possible to selectively transmit a signal ofa desired frequency band by optimizing the shape of the conductorpatterns 103. Since this BPF 101 is a part of the whole pattern wiringformed on the dielectric board 102 and has a flat structure, the BPF 101can be collectively formed when forming the pattern wiring on thedielectric board 102, for example, by print processing, lithographyprocessing or the like.

In the circuit board 100 shown in FIG. 1, since the BPF 101 has a flatstructure and the conductor patterns 103 are arrayed with an overlap ofsubstantially ¼ of a passing wavelength λ, the length of the conductorpatterns 103 is prescribed by the passing wavelength λ. In the circuitboard 100, the conductor patterns 103 need to have a certain length andit is difficult to reduce the occupied area of the conductor patterns103. Therefore, area-saving is limited.

Thus, in a circuit board 100 shown in FIGS. 2A to 2D, it is proposed tosave the area by using a BPF 111 as a filter element that requires asmaller occupied area. This BPF 111 has a so-called tri-plate structure,which is a three-layer structure in which resonator conductor patterns114 arranged substantially parallel to each other are formed in an innerlayer of a multilayer board 113 such as a multilayer printed board.

Specifically, in the BPF 111, a pair of resonator lines 114 has animpedance step structure in which low-impedance lines (thick lines) 115and high-impedance lines (thin lines) 116 are connected with each othernear a substantially central part in the longitudinal direction, andfeeder wirings 117 are connected to parts near substantially centralparts of the high-impedance lines 116, respectively, as shown in FIG.2C. In this BPF 111, the pair of resonator lines 114 is held between twoground parts 118 a, 118 b as ground conductors from above and below,with insulating layers 112 provided between the resonator lines 114 andthe ground parts 118 a, 118 b. In this BPF 111, the two ground parts 118a, 118 b are connected with each other in the form of interlayerconnection by via-holes 119 surrounding the pair of resonator lines 114,and the resonator lines 114 in the layer are shielded by the groundparts 118 a, 118 b and the via-holes 119.

In this filter circuit 110, the pair of resonator lines 114 isconstructed as lines having a length substantially ¼ of the passingwavelength λ are arranged in parallel and then capacitive-coupled. Asthe pair of resonator lines 114 has the impedance step structure, thelength of the lines arranged in parallel can be made equal to or lessthan the passing wavelength λ, and the occupied area of the BPF 111 canbe reduced to realize miniaturization.

In this filter circuit 110, when the BPF 111 is shown in the form of anequivalent circuit, parallel resonance circuits are capacitive-coupled,as shown in FIG. 3. Specifically, a parallel resonance circuit PR1including a capacitor C1 and an inductance I1 connected between one ofthe two resonator lines 114 and the ground parts 118 a, 118 b, and aparallel resonance circuit PR2 including a capacitor C2 and aninductance I2 connected between the other of the two resonator lines 114and the ground parts 118 a, 118 b, are capacitive-coupled via acapacitor C3 generated between the pair of resonator lines 114.

In the above-described filter circuit 110, as the impedance ratiobetween the low-impedance lines 115 and the high-impedance lines 116 ofthe pair of resonator lines 114 is increased, the lines arranged inparallel can be reduced. Therefore, the occupied area of the filterelement can be reduced to realize miniaturization. Specifically, byforming the high-impedance lines 116 that are much thinner than thelow-impedance lines 115, it is possible to further miniaturize thefilter circuit 110.

In the filter circuit 110, since metal layers of the above-describedresonator lines 114 formed by a thick film forming technique such as aplating method are patterned by etching processing or the like, it isdifficult to reduce the thickness of the high-impedance lines 116 to0.075 mm or less, thus limiting the miniaturization.

In this filter circuit 110, when the thickness of the high-impedancelines 116 of the pair of resonator lines 114 is reduced to the minimumpossible level, it is difficult to form the high-impedance lines 116with high accuracy, and reduction in yield and deterioration in filtercharacteristic may occur.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a new filter circuitdevice and a method for manufacturing the same that enable solution tothe problem of the conventional filter circuit device as describedabove.

It is another object of the present invention to provide a filtercircuit device in which deterioration in filter characteristic isprevented and in which the occupied area of a filter element is reducedto realize miniaturization, and a method for manufacturing the same.

A filter circuit device according to the present invention includes: acircuit part in which plural circuit layers are stacked, each circuitlayer including an insulating layer made of a dielectric insulatingmaterial and a wiring layer made of a pattern conductor; and a filterelement in which a first filter line and a second filter line, eachincluding a pair of lines parallel to each other provided in a part ofthe wiring layers of the circuit layers, are formed in different ones ofthe circuit layers so that the lines of each pair are substantiallyparallel to each other in their longitudinal direction, the first filterline and the second filter line being electrically connected at one endwhere they face each other in the direction of stacking of the circuitlayers; wherein in the filter element, the first filter line is formedas a high-impedance line having a smaller thickness and a smaller widththan the second filter line by a thin film forming technique, and thesecond filter line is formed as a low-impedance line by a thick filmforming technique.

In the filter circuit device according to the present invention, sincethe first filter line as the high-impedance line of the filter elementis formed by the thin film forming technique so as to have asignificantly smaller thickness and a significantly smaller width thanthe second filter line as the low-impedance line formed by the thickfilm forming technique, the ratio of impedance between thehigh-impedance line and the low-impedance line can be increased and thelength of each pair of lines formed in the wiring layers of the circuitlayers can be significantly reduced.

In this filter circuit device, since the high-impedance line of thefilter element is formed by the thin film forming technique, a thin linehaving a smaller thickness and less unevenness in size than when thehigh-impedance line is formed by the thick film forming technique isformed with high accuracy.

A method for manufacturing a filter circuit device according to thepresent invention includes: a circuit layer forming step of formingplural circuit layers, each circuit layer including an insulating layermade of a dielectric insulating material and a wiring layer made of apattern conductor; a first line forming step of forming a first filterline including a pair of lines parallel to each other provided in a partof the wiring layer in one of the plural circuit layers; a second lineforming step of forming a second filter line including a pair of linesparallel to each other provided in a part of the wiring layer in anotherone of the circuit layers that is different from the circuit layer wherethe first filter line is formed; a circuit part forming step of forminga circuit part by stacking the plural circuit layers; and an elementforming step of, when stacking the circuit layers, stacking the firstfilter line and the second filter line so as to face each other in sucha manner that the lines of each pair are substantially parallel to eachother in their longitudinal direction, and electrically connecting thefirst filter line and the second filter line at one end where they faceeach other in the direction of stacking of the circuit layers, thusforming a filter element. In the method for manufacturing a filtercircuit device according to the present invention, at the first lineforming step, the first filter line is formed as a high-impedance linehaving a smaller thickness and a smaller width than the second filterline by a thin film forming technique, and at the second line formingstep, the second filter line is formed as a low-impedance line by athick film forming technique.

In the method for manufacturing a filter circuit device according to thepresent invention, since the first filter line as the high-impedanceline of the filter element is formed by the thin film forming techniqueso as to have a significantly smaller thickness and a significantlysmaller width than the second filter line as the low-impedance lineformed by the thick film forming technique, the ratio of impedancebetween the high-impedance line and the low-impedance line can beincreased and the length of each pair of lines constituting the filterelement can be significantly reduced. Thus, a further miniaturizedfilter circuit device can be manufactured.

In this method for manufacturing a filter circuit device, since thehigh-impedance line of the filter element is formed by the thin filmforming technique, the high-impedance line having a smaller thicknessand less unevenness in size than when it is formed by the thick filmforming technique can be formed with high accuracy. Therefore, a filtercircuit device having a filler element in which deterioration in filtercharacteristic is prevented is manufactured at a high yield.

The other object of the present invention and specific advantagesprovided by the present invention will be further clarified by thefollowing description of an embodiment referring to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing a circuit board having aband-pass filter of a flat structure.

FIGS. 2A to 2D show a filter circuit having a band-pass filter of atri-plate structure. FIG. 2A is a partly perspective longitudinalsectional view. FIG. 2B is a plan view showing a ground part of an upperlayer. FIG. 2C is a plan view showing resonator lines. FIG. 2D is a planview showing a ground part of a lower layer.

FIG. 3 is a circuit diagram showing the band-pass filter of thetri-plate structure in the form of an equivalent circuit.

FIG. 4 is a longitudinal sectional view showing the state where a filtercircuit device according to the present invention is mounted on a baseboard.

FIG. 5 is a partly perspective view showing a filter elementconstituting the filter circuit device.

FIGS. 6A to 6E show the filter element provided in the filter circuitdevice. FIG. 6A is a plan view showing a third ground part. FIG. 6B is aplan view showing a second resonator line. FIG. 6C is a plan viewshowing a first ground part. FIG. 6D is a plan view showing a firstresonator line. FIG. 6E is a plan view showing a second ground part.

FIG. 7 is a process view showing a process of manufacturing a firstcircuit part constituting the filter circuit device.

FIGS. 8 to 15 sequentially show the process of manufacturing the firstcircuit part constituting the filter circuit device. FIG. 8 is alongitudinal sectional view showing a core board. FIG. 9 is alongitudinal sectional view showing the state where a first wiring layerand a second wiring layer are formed. FIG. 10 is a longitudinalsectional view showing the state of joining a first resin-attached metalfilm and a second resin-attached metal film to the core board. FIG. 11is a longitudinal sectional view showing the sate where a via-hole isformed in the first resin-attached metal film and the secondresin-attached metal film. FIG. 12 is a longitudinal sectional viewshowing a circuit part intermediate body. FIG. 13 is a longitudinalsectional view showing the state of joining a third resin-attached metalfilm and a fourth resin-attached metal film to the circuit partintermediate body. FIG. 14 is a longitudinal sectional view showing thestate where the third resin-attached metal film and the fourthresin-attached metal film are joined to the circuit part intermediatebody. FIG. 15 is a longitudinal sectional view showing the first circuitpart.

FIG. 16 is a process view showing a process of manufacturing a secondcircuit part constituting the filter circuit device.

FIGS. 17 to 23 sequentially show the process of manufacturing the secondcircuit part constituting the filter circuit device. FIG. 17 is alongitudinal sectional view showing the state where a first insulatinglayer is formed on a forming surface. FIG. 18 is a longitudinalsectional view showing the state where a metal film is formed on thefirst insulating layer. FIG. 19 is a longitudinal sectional view showingthe state where a first conductor layer is formed. FIG. 20 is alongitudinal sectional view showing the state where a via-hole is formedin a first unit wiring layer. FIG. 21 is a longitudinal sectional viewshowing the state where a second unit wiring layer is formed on thefirst unit wiring layer. FIG. 22 is a longitudinal sectional viewshowing the state where a third unit wiring layer is formed on thesecond unit wiring layer. FIG. 23 is a longitudinal sectional viewshowing the state where the circuit part is formed on the first circuitpart.

FIG. 24 is a longitudinal sectional view showing a process ofmanufacturing the filter circuit device according to the presentinvention and showing the state where a resist layer is formed.

FIG. 25 is a longitudinal section view showing the filter circuit devicemanufactured by the manufacturing method according to the presentinvention.

FIG. 26 is a longitudinal sectional view showing the state where thefilter circuit device according to the present invention is mounted on abase board.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described in detailwith reference to the drawings.

A filter circuit device to which the present invention is appliedconstitutes a high-frequency circuit used in a transmitting/receivingunit provided in a portable communication terminal device or the likeand adapted for processing a high-frequency signal. The filter circuitdevice 1 has a first circuit part 2, a second circuit part 3 formed on amajor surface (hereinafter referred to as forming surface) 2 a of thefirst circuit part 2, and a filter element 4 formed to extend onto thefirst circuit part 2 and the second circuit part 3, as shown in FIGS. 4and 5.

In the filter circuit device 1, the first circuit part 2 has a wiringpart of a power system and a control system with respect to the secondcircuit part 3 formed on the forming surface 2 a, and a mounting surface2 b with respect to a base board 90. In the filter circuit device 1, asemiconductor component 91 such as a semiconductor chip, an IC(integrated circuit) chip or an LSI (large-scaled integrated circuit)chip is mounted on a mounting surface 3 a, which is the surface of thesecond circuit part 3, and a shield cover 92 is attached to seal thewhole mounting surface 3 a.

The first circuit part 2 uses a core board 5 as its core, which is adual-side board. The core board 5 has a structure in which plural resinlayers and wiring layers are stacked on its two major surfaces. In thefirst circuit part 2, the core board 5 includes a resin layer 5 a andmetal layers 5 b formed on both major surfaces of the resin layer 5 a,as shown in FIG. 8, which will be described later. As these metal layers5 b are patterned, for example, by etching processing, one of the metallayers becomes a first wiring layer 6 and the other becomes a secondwiring layer 7.

The resin layer 5 a constituting the core board 5 is made of adielectric insulating material having low Tan δ at a low dielectricconstant, that is, an excellent high-frequency characteristic.Specifically, the resin layer 5 a is made of polyphenylene ether (PPE),bismaleidetriazine (BT-resin), polytetrafluoroethylene, polyimide,liquid crystal polymer (LCP), polynorbornene (PN B), ceramics, or amixture of ceramics and an organic material. The core board 5 hasmechanical rigidity, heat resistance, and chemical resistance. Forexample, an epoxy-based copper-clad board FR-5 or the like may be used,which is less expensive than the board material made of theabove-described materials.

The metal layers 5 b provided in the core board 5, that is, the firstwiring layer 6 and the second wiring layer 7, are made of highlyconductive metal layers such as Cu. These wiring layers are formed onboth major surfaces of the resin layer by a thick film forming techniquesuch as a plating method and patterned by etching processing or thelike.

In the first circuit part 2, a first resin-attached metal film 8 isjoined onto the first wiring layer 6 of the core board 5, and a secondresin-attached metal film 9 is joined onto the second wiring layer 7.The first resin-attached metal film 8 includes a resin layer 8 a and ametal film 8 b. The resin layer 8 a is joined to face the first wiringlayer 6 of the core board 5, and the metal film 8 b is patterned byetching processing or the like, thus forming a third wiring layer 10,which is a pattern conductor. The second resin-attached metal film 9includes a resin layer 9 a and a metal film 9 b. The resin layer 9 a isjoined to face the second wiring layer 7 of the core board 5, and themetal film 9 b is patterned by etching processing or the like, thusforming a fourth wiring layer 11, which is a pattern conductor.

The resin layers 8 a, 9 a of the first resin-attached metal film 8 andthe second resin-attached metal film 9 are made of a material having lowTan δ at a low dielectric constant and an excellent high-frequencycharacteristic, similarly to the resin layer 5 a of the core board. Themetal layers 8 b, 9 b constituting first resin-attached metal film 8 andthe second resin-attached metal film 9, that is, the third wiring layer10 and the fourth wiring layer 11, are made of highly conductive Culayers. These wiring layers are formed on major surfaces of the resinlayers 8 a, 9 b by a thick film forming technique such as a platingmethod and patterned by etching processing or the like.

In the first circuit part 2, resin-attached metal films, not shown here,are joined onto the third wiring layer 10 of the first resin-attachedmetal film 8 and the fourth wiring layer 11 of the second resin-attachedmetal film 9 so that the resin-layer sides of these resin-attached metalfilms face the wiring layers. These resin-attached metal films arepolished until the third wiring layer 10 and the fourth wiring layer 11are exposed. Thus, in the first circuit part 2, the resin layer isembedded between the pattern conductors of the third wiring layer 10 andthe fourth wiring layer 11, and the surface where the third wiring layer10 and the fourth wiring layer 11 are exposed is flattened with highaccuracy.

The first circuit part 2 is constructed as described above. In thisdescription, since the second circuit part 3 is formed on the side ofthe third wiring layer 10 that is flattened with high accuracy, thesurface where the third wiring layer 10 is exposed is regarded as theforming surface 2 a. Alternatively, the second circuit part 3 may beformed on the major surface on the side where the fourth wiring layer 11is exposed, of the first circuit part 2. The major surface opposite tothe forming surface 2 a, that is, the major surface on the side wherethe fourth wiring layer 11 is exposed, is regarded as the mountingsurface 2 b to face and be mounted on the base board 90.

The second circuit part 3 has a structure in which plural resin layersand wiring layers are stacked on the forming surface 2 a of the firstcircuit part 2, which is flattened with high accuracy. Specifically, thesecond circuit part 3 has a structure in which a first insulating layer12, a first conductor layer 13, a second insulating layer 14, a secondconductor layer 15, a third insulating layer 16 and a third conductorlayer 17 are sequentially stacked on the forming surface 2 a of thefirst circuit part 2.

In the second circuit part 3, the plural insulating layers are made of amaterial having low Tan δ at a low dielectric constant and an excellenthigh-frequency characteristic, similarly to the resin layer 5 a of thecore board. In the second circuit part 3, the plural conductor layers,made of highly conductive metal layers such as Cu, are formed betweenthe insulating layers, respectively, by a thin film forming techniquesuch as a sputtering method or a chemical vapor deposition (CVD) method,and are patterned by etching processing or the like. In the secondcircuit part 3, plural via-holes 18 for electrically connecting theplural conductor layers are provided between these plural conductorlayers, and these via-holes 18 connect the plural conductor layers byinterlayer connection.

The filter element 4 is designed on the basis of a distributed constantdesign using a microstrip line or strip line, instead of a lumpedconstant design using a chip component such as an inductor or acapacitor. In this filter element 4, a pair of first resonator lines(hereinafter referred to as first lines) 19 a, 19 b provided in a partof the third wiring layer 10 in the first circuit part 2, and a pair ofsecond resonator lines (hereinafter referred to as second lines) 20 a,20 b provided in a part of the conductor layer that is second from theforming surface 2 a in the second circuit part 3, that is, in a part ofthe second conductor layer 15, are stacked and these pairs of lines areselectively connected by connecting parts 21 including via-holes orthrough-holes, as shown in FIG. 5 and FIGS. 6A to 6E.

In the filter element 4, a first ground part 22 provided in a part ofthe conductor layer that is first from the forming surface 2 a in thecircuit part 2, that is, in a part of the first conductor layer 13, isprovided between the stacked first lines 19 a, 19 b and second lines 20a, 20 b. This first ground part 22 serves as a ground conductor for thesecond lines 20 a, 20 b.

In the filter element 4, the first lines 19 a, 19 b are linearly formedand arranged substantially parallel to each other so that they face eachother in the direction of their width, as shown in FIG. 6D. In thefilter element 4, similarly to the first lines 19 a, 19 b, the secondlines 20 a, 20 b are linearly formed and arranged substantially parallelto each other so that they face each other in the direction of theirwidth, as shown in FIG. 6B. In the filter element 4, the second line 20a is formed right above the first line 19 a, and the second line 20 b isformed right above the first line 19 b. The lines facing each other inthe direction of the thickness of the filter circuit device 1 areelectrically connected with each other at one end by the connectingparts 21. Specifically, as shown in FIGS. 6B, 6C and 6D, the first line19 a and the second line 20 a are connected at one end and the firstline 19 b and the second line 20 b are connected at one end by theconnecting parts 21.

In the filter element 4, on the pair of second lines 20 a, 20 b, feederparts 23 protruding in the direction opposite to the facing direction ofthe second lines 20, 20 b are provided from substantially central partsin the longitudinal direction of the second lines 20 a, 20 b, as shownin FIG. 6B. On the second lines 20 a, 20 b, short-circuit via-holes 24for connecting to the first ground part 22 are provided at the other endthat is opposite to the one end where the second lines 20 a, 20 b areconnected with the connecting parts 21, as shown in FIG. 5.

In the filter element 4, a second ground part 25 a is formed right belowthe first lines 19 a, 19 b, that is, in a part of the first wiring layer6 in the first circuit part 2, and a third ground part 25 b is formedright above the second lines 20 a, 20 b, that is, in part of the thirdconductor layer 17, which is the third conductor layer from the formingsurface 2 a in the second circuit part 3. In the filter element 4,plural shield parts 26 including via-holes or through-holes for makingelectric interlayer connection between the first ground part 22, thesecond ground part 25 a and the third ground part 25 b are formed aroundthe first lines 19 a, 19 b and the second lines 20 a, 20 b. Thus, in thefilter element 4, the second ground part 25 a, the third ground part 25b and the shield parts 26 shield the first lines 19 a, 19 b and thesecond lines 20 a, 20 b.

Specifically, in the filter element 4, the first lines 19 a, 19 b areformed as low-impedance lines in a part of the third wiring layer 10 insuch a manner that the first lines 19 a, 19 b have a length ofapproximately 7 mm, a width of approximately 1 mm and a thickness morethan 100 μm and are exposed from the forming surface 2 a of the firstcircuit part 2 having a dielectric insulating material with a relativedielectric constant of approximately 3.8 and having a thickness ofapproximately 0.7 mm. In this filter element 4, the second lines 20 a,20 b are formed as high-impedance lines in a part of the secondconductor layer 15 on the second insulating layer 14 formed bydepositing a dielectric insulating material with a relative dielectricconstant of approximately 2.65 to a thickness of approximately 20 μm sothat the second lines 20 a, 20 b have a length of approximately 7 mm, awidth of approximately 50 μm and a thickness less than 50 μm.

In the filter circuit device 1 of the above-described structure, thepair of second lines 20 a, 20 b, as the high-impedance lines of thefilter element, is formed in a part of the second conductor layer 15 ofthe second circuit part 3, and this second conductor layer 15 is formedby a thin film forming technique such as a sputtering method or a CVDmethod. Therefore, in this filter circuit device 1, the pair of secondlines 20 a, 20 b can be accurately formed to have a significantlysmaller thickness than that of the pair of first lines 19 a, 19 b as thelow-impedance lines formed by a thick film forming technique such as aplating method.

In this filter circuit device 1, since the impedance ratio between thepair of second lines 20 a, 20 b accurately formed to have asignificantly smaller thickness by the thin film forming technique andthe pair of first lines 19 a, 19 b formed by the thick film formingtechnique can be increased in the filter element 4, the length of thesepairs of resonator lines can be significantly reduced andminiaturization is realized.

In this filter circuit device 1, since the pair of thin second lines 20a, 20 b is by the thin film forming technique in the filter element 4,it is possible to accurately form the pair of second lines 20 a, 20 bhaving a significantly smaller thickness and less unevenness inthickness than in the case of forming resonator lines by a thick filmforming technique such as a plating method. Thus, deterioration infilter characteristic is prevented.

In this filter circuit device 1, the filter element 4 has a structure inwhich the pair of first lines 19 a, 19 b and the pair of second lines 20a, 20 b are stacked via the dielectric insulating material, with thepairs of lines connected each other at one end in their longitudinaldirection by the connecting parts 21, that is, a structure in which apair of resonator lines is bent at the connecting parts 21 so as tosandwich the dielectric insulating material.

Therefore, in the filter circuit device 1, the length of the first lines19 a, 19 b and the second lines 20 a, 20 b in the filter element 4 canbe reduced to half the length of a pair of resonator lines where theresonator lines used for the same frequency band as the filter element 4are formed in a planar form. It is therefore possible to reduce theoccupied area of the filter element 4 and realize miniaturization.

In this filter circuit device 1, since the pair of second lines 20 a, 20b as high-impedance lines of the filter element 4 is provided on thesecond insulating layer 14 made of the dielectric insulating materialhaving a lower relative dielectric constant than that of the firstcircuit part 2 where the pair of first lines 19 a, 19 b as low-impedancelines is formed, the length of these pairs of resonator lines can befurther reduced.

In this filter circuit device 1, the first ground part 22 is providedbetween the layers where the pair of first lines 19 a, 19 b and the pairof second lines 20 a, 20 b are formed, in the filter element 4, and thefirst ground part 22 functions as a shield between the pair of firstlines 19 a, 19 b and the pair of second lines 20 a, 20 b. Therefore,deterioration in filter characteristic due to interference between thepairs of resonator conductors is prevented.

A method for manufacturing the above-described filter circuit devicewill now be described.

To manufacture the filter circuit device 1, the first circuit part 2 isformed first. The process of preparing the first circuit part 2 will bedescribed with reference to FIGS. 7 to 15.

In the first circuit part preparation process, as shown in FIG. 7, acircuit part intermediate body 32 is prepared through the followingsteps: a first wiring layer forming step s-1 of forming plural via-holes30 in the front and back major surfaces of the core board 5, penetratingthe first wiring layer 6, the second wiring layer 7 and the core board5; a first resin-attached metal film joining step s-2 of joining thefirst resin-attached metal film 8 and the second resin-attached metalfilm 9 to the front and back major surfaces of the core board 5; avia-hole forming step s-3 of forming via-holes 31 in the resin-attachedmetal films 8 and 9; and a second wiring layer forming step s-4 offorming the third wiring layer 10 in the metal layer 8 b of the firstresin-attached metal film 8 and forming the fourth wiring layer 11 inthe metal layer 9 b of the second resin-attached metal film 9.

In the first circuit part preparation process, the first circuit part 2is prepared through the following steps: a second resin-attached metalfilm joining step s-5 of joining a third resin-attached metal film 33covering the third wiring layer 10 and a fourth resin-attached metalfilm 34 covering the fourth wiring layer 11 to the circuit partintermediate body 32; and a polishing step s-6 of polishing the thirdresin-attached metal film 33 and the fourth resin-attached metal film 34to form the forming surface 2 a where the third wiring layer 10 isexposed.

When preparing the first circuit part 2 by the above-described process,the core board 5 is prepared in which the metal layer 5 b made of ahighly conductive metal layer such as Cu is formed on the front and backmajor surfaces of the resin layer 5 a by a plating method or the like,as shown in FIG. 8. The resin layer 5 a of the core board 5 is made of adielectric insulating material having an excellent high-frequencycharacteristic.

Next, the first wiring layer forming step s-1 is performed on the coreboard 5, as shown in FIG. 9. In the core board 5, hole-making processingwith a drill, laser or the like is performed to form plural via-holes 30a. After the inner walls of these via-holes 30 a are, for example,plated and conductive paste 30 is embedded therein, cover forming basedon plating or the like is performed. Thus, the via-holes 30 forelectrically connecting the metal layers 5 b formed on the front andback major surfaces of the resin layer 5 a are formed. Since theapertures of the via-holes 30 a are covered by plating or the like afterthe conductive paste 30 b is embedded in the via-holes 30 a, via-holesor the like can be formed immediately above the via-holes 30.

As photolithography processing or the like is performed on the metallayers 5 b formed on the front and back major surfaces of the resinlayer 5 a of the core board 5, the metal layers 5 b are patterned toform the first wiring layer 6 and the second wiring layer 7 as patternconductors on the front and back major surfaces on the resin layer 5 a.At the first wiring layer forming step s-1, the second ground part 25 ain the filter element 4 is formed together with the other patternconductors in the first wiring layer 6.

Next, the first resin-attached metal film joining step s-2 is performedon the core board 5, as shown in FIG. 10. To the core board 5, the firstresin-attached metal film 8 is joined to cover the first wiring layer 6and the second resin-attached metal film 9 is joined to cover the secondwiring layer 7. In the first resin-attached metal film 8 and the secondresin-attached metal film 9, the metal films 8 b, 9 b made of a highlyconductive metal such as Cu are formed by plating or the like on theentire one-side major surfaces of the resin layers 8 a, 9 a made of adielectric insulating material having an excellent high-frequencycharacteristic. The first resin-attached metal film 8 and the secondresin-attached metal film 9 are joined onto the first wiring layer 6 andthe second wiring layer 7 of the core board 5, for example, by anadhesive resin or a so-called prepreg resin. The first resin-attachedmetal film 8 and the second resin-attached metal film 9 can be joinedwithout using a prepreg resin, if the resin layers 8 a, 9 a are made ofa thermoplastic resin.

Next, the via-hole forming step s-3 is performed on the firstresin-attached metal film 8 and the second resin-attached metal film 9,as shown in FIG. 11. In the first resin-attached metal film 8 and thesecond resin-attached metal film 9, the via-holes 31 are formed,similarly to the via-holes 30 penetrating the core board 5.Specifically, a via-hole 31 a for electrically connecting the firstwiring layer 6 with the metal film 8 b of the first resin-attached metalfilm 8 is formed in the first resin-attached metal film 8, and avia-hole 31 b for electrically connecting the second wiring layer 7 withthe metal film 9 b of the second resin-attached metal film 9 is formedin the second resin-attached metal film 9. At the via-hole forming steps-3, a shield via-holes 26 a is formed in the first resin-attached metalfilm 8, similarly to the via-hole 31 a, as a pair of the shield part 26to surround the region where the filter element 4 is formed.

Next, the second wiring layer forming step s-4 is performed on the firstresin-attached metal film 8 and the second resin-attached metal film 9,as shown in FIG. 12. In the first resin-attached metal film 8 and thesecond resin-attached metal film 9, the third wiring layer 10 and thefourth wiring layer 11 are formed by a process similar to the process offorming the first wiring layer 6 and the second wiring layer 7.Specifically, as photolithography processing or the like is performed onthe metal films 8 b, 9 b, the metal films 8 b, 9 b are patterned, thusforming the third wiring layer 10 as a pattern conductor on the resinlayer 8 a of the first resin-attached metal film 8 and forming thefourth wiring layer 11 as a pattern conductor on the resin layer 9 a ofthe second resin-attached metal film 9.

At the second wiring layer forming step s-4, in the third wiring layer10, the pair of first lines 19 a, 19 b is formed together with the otherpattern conductors, immediately above the second ground part 25 aprovided in a part of the first wiring layer 6. Since the pair of firstlines 19 a, 19 b is provided in a part of the third wiring layer 10formed by a thick film forming technique such as a plating method, thepair of first lines 19 a, 19 b has a thickness more than 100 μm. Thefourth wiring layer 11 becomes a power supply part from a mother boardor an input/output terminal part 35 functioning as an input/output partfor electric signals, when the filter circuit device 1 is mounted on thebase board 90.

Next, the second resin-attached metal film joining step s-5 is performedon the circuit part intermediate body 32, as shown in FIGS. 13 and 14.To the circuit part intermediate body 32, the third resin-attached metalfilm 33 is joined to cover the third wiring layer 10 and the fourthresin-attached metal film 34 is joined to cover the fourth wiring layer11. In the third resin-attached metal film 33 and the fourthresin-attached metal film 34, similar to the above-describedresin-attached metal films, metal films 33 a, 34 a made of a highlyconductive metal such as Cu are formed by plating or the like on entireone-side major surfaces of resin layers 33 b, 34 b made of a dielectricinsulating material having an excellent high-frequency characteristic.

The third resin-attached metal film 33 and the fourth resin-attachedmetal film 34 are joined to both major surfaces of the circuit partintermediate body 32 by prepreg resins on the third wiring layer 10 andthe fourth wiring layer 11. The third resin-attached metal film 33 andthe fourth resin-attached metal film 34 can be joined without using theprepreg resins, if the resin layers 33 b, 34 b are made of athermoplastic resin.

Next, the polishing step s-6 is performed on the third resin-attachedmetal film 33 and the fourth resin-attached metal film 34, as shown inFIG. 15. The entire major surfaces where the metal films 33 a, 34 aexist, of the third resin-attached metal film 33 and the fourthresin-attached metal film 34, are polished by a polisher made of, forexample, a mixture of alumina and silica.

Specifically, polishing is performed on the third resin-attached metalfilm 33 until the third wiring layer 10 is exposed. On the fourthresin-attached metal film 34, polishing is performed in such a manner asto leave the resin layer 34 b to a predetermined thickness of Δx withoutexposing the fourth wiring layer 11. Thus, on the surface where thethird wiring layer 10 is exposed, the resin layer 33 b is embeddedbetween the pattern conductors, forming the forming surface 2 a that isflattened with high accuracy. In the above-described manner, the firstcircuit part 2 is prepared in which the first lines 19 a, 19 b of thefilter element 4 are formed on the forming surface 2 a. In this firstcircuit part 2, a dielectric insulating material having a relativelyhigh relative dielectric constant of approximately 3.8 is used for eachresin layer.

In this first circuit part 2, the second circuit part 3 is to be formedon the third wiring layer 10 in a second circuit part preparationprocess, which will be described later. Since the second circuit part 3protects the third wiring layer 10 from chemical, mechanical and thermalloads, the resin layer 33 b is polished until the third wiring layer 10is exposed. In the first circuit part 2 of the above-describedstructure, the third wiring layer 10 constitutes a wiring part for apower system, a wiring part for a control system or a ground part withrespect to the second circuit part 3 in the second circuit partpreparation process, which will be described later.

In the first circuit part 2 of the above-described structure, the fourthwiring layer 11 is protected by the remaining resin layer 34 b fromchemical, mechanical and thermal loads in the second circuit partpreparation process, which will be described later. In the first circuitpart 2, as the above-described resin layer 34 b is cut and removed afterthe second circuit part 3 is formed, the fourth wiring layer 11 isexposed to constitute the input/output terminal part 35.

In the above-described first circuit part preparation process, since aprocess similar to a conventional process of preparing a multilayerboard is used as the process of preparing the circuit part intermediatebody 32, the multilayer board preparation process can be used as it isand high productivity is realized. The first circuit part preparationprocess is not limited to the above-described process and variousconventional multilayer board preparation processes may be used.

The process of preparing the second circuit part 3 will now be describedin detail with reference to FIGS. 16 to 22. As shown in FIG. 16, thesecond circuit preparation process includes the following steps: a firstinsulating layer forming step s-7 of forming the first insulating layer12 on the forming surface 2 a of the first circuit part 2; a firstconductor layer forming step s-8 of forming the first conductor layer 13on the surface of the first insulating layer 12; and a via-hole formingstep s-9 of forming the via-holes 18 in a first unit wiring layer 36including the first insulating layer 12 and the first conductor layer13.

In the second circuit part preparation process, the second circuit part3 is prepared through the following steps: a second unit wiring layerforming step s-10 of forming a second unit wiring layer 37 including thesecond insulating layer 14 and the second conductor layer 15, on thefirst unit wiring layer 36; and a third unit wiring layer forming steps-11 of forming a third unit wiring layer 38 including the thirdinsulating layer 16 and the third conductor layer 17, on the second unitwiring layer 37.

In preparing the second circuit part 3 by the above-described process,first, the first insulating layer forming step s-7 is performed on theforming surface 2 a of the first circuit part 2, as shown in FIG. 17. Onthe entire forming surface 2 a of the first circuit part 2, a dielectricinsulating material having low Tan δ at a low dielectric constant and anexcellent high-frequency characteristic, and the first insulating layer12 made of this dielectric insulating material is formed. The dielectricinsulating material forming the first insulating layer 12 may be, forexample, benzocyclobutene (BCB), polyimide, polynorbornene (PNB), liquidcrystal polymer (LCP), epoxy resin, acrylic resin or the like. In thisdescription, the first insulating layer 12 is made of a dielectricinsulating material having a low relative dielectric constant ofapproximately 2.65. The method for forming the first insulating layer 12may be, for example, a spin coat method, a curtain coat method, a rollcoat method, a dip coat method or the like, in which the thickness ofthe layer to be formed can be controlled relatively easily.

Next, the first conductor layer forming step s-8 is performed on thefirst insulating layer 12, as shown in FIG. 18. On the entire surface ofthe first insulating layer 12, a metal film 39 is formed by a thin filmforming technique such as a sputtering method or a CVD method. Thismetal film 39 is made of a highly conductive metal such as Cu with athickness less than 50 μm.

Next, the metal film 39 is patterned, as shown in FIG. 19. The metalfilm 39 thus becomes the first conductor layer 13. Specifically, asphotolithography processing or the like is performed on the metal film39, the metal film 39 is patterned to form the first conductor layer 13as a pattern conductor on the first insulating layer 12. At this point,in a part of the first conductor layer 13, the first ground part 22 ofthe filter element 4 is formed together with the other patternconductors. In this manner, the first unit wiring layer 36 including thefirst insulating layer 12 and the first conductor layer 13 is formed.

Next, the via-hole forming step s-9 is performed on the first unitwiring layer 36, as shown in FIG. 20. On the first unit wiring layer 36,hole-making processing using a drill, laser or the like is performed andplural via-holes 18 a are thus formed. After the inner walls of thesevia-holes 18 a are plated, for example, and conductive paste 18 b isembedded therein, cover forming with a metal film is carried out by asputtering method, a CVD method or the like. The via-holes 18 forelectrically connecting to the third wiring layer 10 are thus formed.Since the apertures of the via-holes 18 a are covered with a metal filmor the like after the conductive paste 18 b is embedded in the via-holes18 a, via-holes or the like can be formed immediately above thevia-holes 18.

At this via-hole forming step s-9, connection via-holes 21 a as a partof the connecting parts 21 of the filter element 4 are formed, similarlyto the via-holes 18, in the first unit wiring layer 36 so as to beconnected with one end of the pair of first lines 19 a, 19 b. In thefirst unit wiring layer 36, plural shield via-holes 26 b as a part ofthe shield part 26 of the filter element 4 are formed, similarly to thevia-holes 18, immediately above the shield via-holes 26 a.

Next, the second unit wiring layer forming step s-10 is performed on thefirst unit wiring layer 36, as shown in FIG. 21. On the first unitwiring layer 36, the second unit wiring layer 37 including the secondinsulating layer 14 and the second conductor layer 15 is formed, usingmaterials and processes similar to those of the first insulating layer12 and the first conductor layer 13. The via-holes 18 are also formed inthe second unit wiring layer 37 by a process similar to the via-holeforming step s-9.

At the second unit wiring layer forming step s-10, in the secondconductor layer 15, the pair of second lines 20 a, 20 b is formedtogether with the other pattern conductors, facing the pair of firstlines 19 a, 19 b provided in a part of the third wiring layer 10. Sincethe pair of second lines 20 a, 20 b is provided in a part of the secondconductor layer 15 formed by a thin film forming technique such as asputtering method or a CVD method, the second lines 20 a, 20 b have athickness less than 50 μm.

At the second unit wiring layer forming step s-10, in the secondconductor layer 15, the feeder parts 23, not shown in FIG. 21, areformed together with the other pattern conductors, protruding in thedirection opposite to the facing direction of the pair of second lines20 a, 20 b from substantially central parts in the longitudinaldirection of the pair of second lines 20 a, 20 b.

At the second unit wiring layer forming step s-10, in the second unitwiring layer 37, upper connection via-holes 21 b as a part of theconnecting parts 21 of the filter element 4 are formed, similarly to thevia-holes 18, and connected to one end of the pair of second lines 20 a,20 b immediately above the lower connection via-holes 21 a formed in thefirst unit wiring layer 36. In the second unit wiring layer 37, theshort-circuit via-holes 24 of the filter element 4, not shown in FIG.21, are formed, similarly to the via-holes 18, so as to make a shortcircuit between the other end of the pair of second lines 20 a, 20 b andthe first ground part 22.

In the second unit wiring layer 37, plural shield via-holes 26 c as apart of the shield part 26 of the filter element 4 are formed, similarlyto the via-holes 18, immediately above the shield via-holes 26 b. Thus,the connecting parts 21 include the lower connection via-holes 21 a andthe upper connection via-holes 21 b.

Next, the third unit wiring layer forming step s-11 is performed on thesecond unit wiring layer 37, as shown in FIG. 22. On the second unitwiring layer 37, the third unit wiring layer 38 including the thirdinsulating layer 16 and the third conductor layer 17 is formed, usingmaterials and processes similar to those of the first insulating layer12 and the third conductor layer 13. The via-holes 18 are also formed inthe third unit wiring layer 38 by a process similar to the via-holeforming step s-9. At the third unit wiring layer forming step s-11, thethird ground part 25 b of the filter element 4 is formed together withthe other pattern conductors in the third conductor layer 17.

At the third unit wiring layer forming step s-11, in the third unitwiring layer 38, plural shield via-holes 26 d as a part of the shieldpart 26 of the filter element 4 are formed, similarly to the via-holes18, immediately above the shield via-holes 26 c. The shield part 26 thusincludes the shield via-holes 26 a to 26 d.

Through the above-described process, the filter element 4 is formed inwhich the pair of first lines 19 a, 19 b provided in a part of the thirdwiring layer 10 of the first circuit part 2 and the pair of second lines20 a, 20 b provided in a part of the second conductor layer 15 of thesecond circuit part 3 are stacked via the dielectric insulatingmaterials. The second circuit part 3 in which the conductor layers aspattern conductors are formed by a thin film forming technique is thusmanufactured.

Next, the resin layer 34 b exposed on the major surface of the firstcircuit part 2 that is opposite to the forming surface 2 a, that is, onthe mounting surface 2 b, is polished using a polisher such as a mixturesolution of alumina and silica, as shown in FIG. 23. In the firstcircuit part 2, the fourth wiring layer 11 is thus exposed on themounting surface 2 b.

Next, resist layers 40 a, 40 b are formed on the entire mounting surface2 b of the first circuit part 2 and the entire major surface on thethird unit wiring layer side of the second circuit part 3, as shown inFIG. 24. At predetermined positions in the resist layers 40 a, 40 b,apertures 41 a, 41 b for exposing the fourth wiring layer 11 and thethird conductor layer 17 are provided by a photolithography method orthe like. In the apertures 41 a, 41 b, electrode terminals 42 a, 42 bmade of Au, Ni or the like are formed by a plating method or the like,as shown in FIG. 22. In the above-described manner, the filter circuitdevice 1 having the filter element 4 extending on the first circuit part2 and the second circuit part 3 is manufactured.

In the above-described method for manufacturing the filter circuitdevice 1, the pair of second lines 20 a, 20 b as the high-impedancelines of the filler element 4 is formed in a part of the secondconductor layer 15 of the second circuit part 3, and the secondconductor layer 15 is formed by a thin film forming technique such as asputtering method or a CVD method. Therefore, in this method formanufacturing the filter circuit device 1, the pair of second lines 20a, 20 b can be accurately formed to have a significantly smallerthickness than that of the pair of first lines 19 a, 19 b as thelow-impedance lines formed by a thick film forming technique such as aplating method.

In the method for manufacturing the filter circuit device 1 according tothe present invention, since the impedance ratio between the pair ofsecond lines 20 a, 20 b accurately formed to have a significantlyreduced thickness by the thin film forming technique and the pair offirst lines 19 a, 19 b formed by the thick film forming technique can beincreased in the filter element 4, the filter circuit device 1 that isminiaturized by significantly reducing the length of these pairs ofresonator lines can be provided.

In the method for manufacturing the filter circuit device 1, since thepair of second lines 20 a, 20 b in the filter element 4 is formed tohave a significantly reduced thickness by the thin film formingtechnique, the pair of second lines 20 a, 20 b having a significantlyreduced thickness and restrained unevenness in thickness can beaccurately formed, in comparison with the case of forming resonatorlines by a thick film forming technique such as a plating method. Thus,the filter circuit device 1 having the filter element 4 in whichdeterioration in filter characteristic is prevented can be manufacturedat a high yield.

The method for manufacturing the filler circuit device 1 provides thefilter circuit device 1 having the filter element 4 of a structure inwhich the pair of first lines 19 a, 19 b and the pair of second lines 20a, 20 b are stacked via the dielectric insulating material and thesepairs of lines are connected at one end in their longitudinal directionby the connecting parts 21, that is, a structure in which a pair ofresonator lines is bent at the connecting parts 21 so as to sandwich thedielectric insulating material.

Therefore, in the method for manufacturing the filter circuit device 1according to the present invention, since the length of the first lines19 a, 19 b and the second liens 20 a, 20 b in the filter element 4 canbe reduced to not more than half the length of resonator lines in thecase where a pair of resonator lines used for the same frequency band asthe filter element 4 are formed in a planar form, the filter circuitdevice 1 that is miniaturized by reducing the occupied area of thefilter element 4 is provided.

In the method for manufacturing the filter circuit device 1, since thepair of second lines 20 a, 20 b as the high-impedance lines of thefilter element 4 is formed on the second insulating layer 14 made of adielectric insulating material having a lower relative dielectricconstant than in the first circuit part 2 where the pair of first lines19 a, 19 b as the low-impedance lines is formed, these pairs ofresonator lines can be further reduced.

In the method for manufacturing the filter circuit device 1, the firstground part 22 of the filter element 4 is formed between the layers ofthe pair of lines 19 a, 19 b and the pair of lines 20 a, 20 b, and thefirst ground part 22 functions as a shield between the pair of firstlines 19 a, 19 b and the pair of second lines 20 a, 20 b. Therefore,there is provided the filter circuit device 1 having the filter element4 in which deterioration in filter characteristic due to interferencebetween these pair of resonator conductor lines is prevented.

The above-described filter circuit device 1 is mounted on the base board90, and the semiconductor components 91 are mounted on the secondcircuit part 3, for example, by a flip-chip method, as shown in FIG. 26.These semiconductor components 91 cover and protect the shield cover 92.When the filter circuit device 1 is mounted on the base board 90, theelectrode terminal 42 a formed on the side of the second circuit part 3constitutes a connecting terminal to be connected to the semiconductorcomponent 91. When the filter circuit device 1 is mounted on the baseboard 90, the electrode terminal 42 b electrically connected to thefourth wiring layer 11 exposed on the mounting surface 2 b of the firstcircuit part 2 functions as a connecting terminal to the base board 90.

While the invention has been described in accordance with a certainpreferred embodiment thereof illustrated in the accompanying drawingsand described in the above description in detail, it should beunderstood by those ordinarily skilled in the art that the invention isnot limited to the embodiment, but various modifications, alternativeconstructions or equivalents can be implemented without departing fromthe scope and spirit of the present invention as set forth and definedby the appended claims.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, the first filterline as the high-impedance line of the filter element is formed by athin film forming technique, and the thickness and width of the firstfilter line can be made significantly smaller than those of thelow-impedance line formed by a thick film forming technique. Therefore,the impedance ratio between the high-impedance line and thelow-impedance line is increased and the length of the pairs of linesconstituting the filter element can be significantly reduced, thusrealizing further miniaturization.

According to the present invention, since the high-impedance line of thefilter element is formed by a thin film forming technique, the thicknessand unevenness in thickness can be reduced in comparison with the casewhere the high-impedance line is formed by a thick film formingtechnique, and a filter circuit device having a filter element with anexcellent filter characteristic can be manufactured at a high yield.

According to the present invention, the filter element having astructure in which the high-impedance line and the low-impedance lineare caused to face each other substantially parallel each other via theinsulating layer in the stacking direction of the circuit layers, and inwhich the high-impedance line and the low-impedance line facing eachother in the stacking direction of the circuit layers are electricallyconnected at one end, that is, the filter element having a structure inwhich a pair of lines is bent at one end via a dielectric insulatingmaterial, is formed.

According to the present invention, the length of the pair of lines inthe filter element having the structure in which the pair of lines isbent at one end can be reduced to not more than half the length of linesin the case where the pair of lines constituting the filter element areformed in a planar form. Therefore, the occupied area of the filterelement can be reduced and the filter circuit device can beminiaturized.

According to the present invention, the high-impedance line of thefilter element are formed in the low-dielectric circuit layer includinga low-dielectric insulating layer made of a low-dielectric insulatingmaterial having a lower dielectric constant than that of the insulatinglayer constituting the circuit layer having the low-impedance line, andthe wiring layer. Therefore, the length of the pair of lines in thefilter element can be further reduced.

1. A filter circuit device comprising: a circuit part in which aplurality of circuit layers are stacked, each circuit layer including aninsulating layer made of a dielectric insulating material and a wiringlayer made of a pattern conductor; and a filter element in which a firstset of parallel filter lines and a second set of parallel filter lines,are respectively provided in different ones of the circuit layers sothat the two sets of filter lines are substantially parallel to eachother in their longitudinal direction, the first filter line set and thesecond filter line set being electrically connected at one end; whereinthe first filter line set is formed by a thin film forming technique asa high-impedance line having a smaller thickness and a smaller widththan the second filter line set and the second filter line set is formedas a low-impedance line by a thick film forming technique.
 2. The filtercircuit device as claimed in claim 1, wherein, the first filter line setis formed in a low-dielectric circuit layer including a low-dielectricinsulating layer made of a low-dielectric insulating material having alower dielectric constant than the insulating layer of the circuit layerwhere the second filter line set is formed.
 3. A method formanufacturing a filter circuit device comprising: a circuit layerforming step of forming a plurality of circuit layers, each circuitlayer including an insulating layer made of a dielectric insulatingmaterial and a wiring layer made of a pattern conductor; a first lineforming step of forming a first filter line including a pair of linesparallel to each other provided in a part of the wiring layer of one ofthe plurality of circuit layers; a second line forming step of forming asecond filter line including a pair of lines parallel to each otherprovided in a part of the wiring layer of another one of the circuitlayers different from the circuit layer where the first filter line isformed; a circuit part forming step of forming a circuit part bystacking the plurality of circuit layers; and a filter element formingstep of, when stacking the plurality of circuit layers, stacking thefirst filter line and the second filter line so as to face each other insuch a manner that the lines of each pair are substantially parallel toeach other in their longitudinal direction, and electrically connectingthe first filter line and the second filter line at one end; wherein atthe first line forming step, the first filter line is formed by a thinfilm forming technique as a high-impedance line having a smallerthickness and a smaller width than the second filter line, and at thesecond line forming step, the second filter line is formed as alow-impedance line by a thick film forming technique.
 4. The method formanufacturing a filter circuit device as claimed in claim 3, wherein atthe first line forming step, the first filter line is formed in alow-dielectric circuit layer including a low-dielectric insulating layermade of a low-dielectric insulating material having a lower dielectricconstant than the insulating layer of the circuit layer where the secondfilter line is formed.